This invention relates to gating for imaging systems, and more particularly, this invention relates to a system and method for obtaining cardiac, peripheral pulse, and respiratory gating signals for improving the timing of image acquisition.
In the medical field, imaging systems are often used to obtain internal physiological information of a subject. For example, a medical imaging system may be used to obtain images of the bone structure, the brain, the heart, the lungs, and various other features of a subject. Medical imaging systems include magnetic resonance imaging (MRI) systems, computed tomography (CT) systems, x-ray systems, ultrasound systems, and various other imaging modalities.
In many applications, it is often desirable to obtain an image at a particular point in a variable cycle, such as a peak of the variable cycle, to analyze behavior at that peak. Gating is an option for characterizing different attributes of an organ for imaging. The most common techniques of gating including cardiac, respiratory, and peripheral pulse gating and these types of gating have uses in numerous medical applications across diagnostic modalities including CT, MR, X-Ray, Ultrasound, and PET-CT.
Cardiac gating, as an example, is an essential component of cardiac imaging while using imaging modalities such as CT, Magnetic resonance (MR) to minimize motion related artifacts. Current method involves using electrocardiogram (EKG) for determining gating pulse. Essentially, the R-wave of the EKG is used for this purpose. FIG. 1 illustrates one cardiac cycle of an EKG signal waveform, including a systole condition, or period, and a diastole condition, or period, of the heart. The portions of the EKG signal labeled Q, R and S are referred to as the QRS complex, in which the R-feature, or R-wave, is the most prominent, highest amplitude, feature of the entire EKG signal. The cardiac cycle is typically defined as beginning with an R-wave and continuing until the occurrence of a next R-wave.
EKG gating selects times when a best image of the heart is available. An EKG machine is connected to a patient. A cardiac cycle period is determined, for example, as a time between R-peaks of the EKG. Using an R-peak as a reference and the determined cardiac cycle period, image acquisition during a scan is gated so that image data is acquired only during periods of a cardiac cycle for which the heart is nearly stationary. Thus, only an electrical system has been utilized for gating medical imaging.